A variety of medical devices are used for chronic, i.e., long-term, delivery of fluid therapy to patients suffering from a variety of conditions, such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, spasticity, or gastroparesis. For example, pumps or other fluid delivery devices can be used for chronic delivery of therapeutic agents, such as drugs to patients. These devices are intended to provide a patient with a therapeutic output to alleviate or assist with a variety of conditions. Typically, such devices are implanted in a patient and provide a therapeutic output under specified conditions on a recurring basis.
One type of implantable fluid delivery device is a drug infusion device that can deliver a fluid medication to a patient at a selected site. A drug infusion device may be implanted at a location in the body of a patient and deliver a fluid medication through a catheter to a selected delivery site in the body. Drug infusion devices, such as implantable drug pumps, commonly include a reservoir for holding a supply of the therapeutic substance, such as a drug, for delivery to a site in the patient. The fluid reservoir can be self-sealing and accessible through one or more ports. A pump is fluidly coupled to the reservoir for delivering the therapeutic substance to the patient. A catheter provides a pathway for delivering the therapeutic substance from the pump to the delivery site in the patient.
Implantable drug delivery or infusion devices are commonly used, for example, when chronic administration of a pharmaceutically active agent or therapeutic substance to a patient is required. An implantable infusion pump-catheter delivery system may be preferred when it is important to deliver the agent to a specific site or when the agent must be administered on a recurrent basis in small, controlled dosages. Precise delivery of appropriate amounts of a fluid agent require accurate characterization of various delivery components of the system, such as the reservoir and catheter. The volume of the catheter, which is proportional to its length, is needed by the clinician or programmer, e.g., when determining the amount of drug needed to prime the entire pump and catheter. Catheter volume is also important when determining the time duration used to maintain a current infusion rate (bridging period) after refilling the pump's reservoir with a different fluid agent or fluid agent concentration to insure that the new infusion rate does not go into effect until the current drug has exited the catheter. Ordinarily, clinicians measure and record the length of catheter during implantation which is then used in calculation priming and bridging durations. However, there are a variety of ways for which this information fails to be recorded or is some how lost leaving clinicians that must manage patient's drug delivery therapies without the catheter length information vital to insuring that the prime and bridge procedures are safe.